Over the past decade, magnetic resonance spectroscopy (MRS) studies have consistently revealed the presence of elevated levels of phosphocholine (PCho) and total choline in various types of cancer cells and solid tumors. It has been shown that PCho levels are correlated with the degree of malignancy in cancer, and that PCho levels decrease in response to successful chemotherapeutic treatment or gene silencing by siRNA. Increased expression levels of PCho have been associated with the up-regulation of choline transport and choline kinase activity, as well as increased catabolism mediated by elevations in phospholipase C (PLC) activity. However the relative contributions of the anabolic and catabolic pathways of PCho formation have not been determined.
Accordingly, a need exists in the art for a reliable method to monitor the activation of phospholipase in vivo.